In cutting, grinding, or the like of a magnetic material which is represented by a metal material, particularly, a steel material, scrap, chips, or the like which is discharged along with coolant liquid are separated from the liquid and recovered. Since the scrap, chips, or the like have various shapes, various magnetic separation (recovery) devices have been developed from the viewpoint of recovery efficiency.
For example, PTL 1 discloses a rotating-drum type magnetic separator in the related art. FIG. 1 shows a configuration of the rotating-drum type magnetic separator in the related art and is a cross-sectional view at a surface perpendicular to a rotational axis of a rotating drum. As shown in FIG. 1, in the rotating-drum type magnetic separator 1 in the related art, a liquid reservoir portion 10 which stores coolant liquid in a box type main body is provided. In order to divide the liquid reservoir portion 10 into two, a rotating drum 3 is supported in an approximately horizontal direction in the vicinity of the center portion of the main body. The rotating drum 3 is a cylindrical body which is formed of a nonmagnetic material such as stainless steel, and an inner cylinder 5, in which a plurality of magnets 4, 4, . . . are disposed on the outer circumferential surface in a predetermined arrangement, is coaxially fixed to the inner portion of an outer cylinder. Polarities of the plurality of magnets 4, 4, . . . are disposed so as to generate a predetermined magnetic flux in the vicinity of the outer circumference surface of the rotating drum 3, so that scrap, chips, or the like which are magnetic bodies contained in the coolant liquid are magnetically attached.
In PTL 1, the plurality of magnets 4, 4, . . . are disposed between a portion in which the rotating drum 3 starts to be immersed in the liquid reservoir portion 10 and the top, that is, on the inner cylinder 5 corresponding to a portion equivalent to approximately ¾ of the outer circumferential surface of the rotating drum 3. The magnet 4 is not disposed on the inner cylinder 5 in the portion corresponding to the remaining approximately ¼, and a magnetic force is not applied on the portion.
Sludge, which is adsorbed on the outer circumference surface of the rotating drum 3 on the bottom portion of the liquid reservoir portion 10 by application of the magnetic force of the plurality of magnets 4, 4, . . . is transported to the top of the rotating drum 3 according to the rotation of the rotating drum 3. When the transported sludge passes through the top, adsorption forces generated due to the magnetic forces of the plurality of magnets 4, 4, . . . are lost, and the sludge is scratched away by a scraper 7 abutting on the rotating drum 3 and is recovered. A squeezing roller 6, in which an elastic body such as rubber is disposed on the surface, is provided in the vicinity of the top of the rotating drum 3, and the squeezing roller 6 is abutted on the outer circumference surface of the rotating drum 3 by a predetermined pressing force. The adsorbed sludge passes through between the rotating drum 3 and the squeezing roller 6, and thus, liquid contained in the sludge is squeezed, and only the scrap, chips, or the like is separated at the position in which the magnetic force does not reach.
In order to suppress the amount of accumulated ground particles which cannot be recovered, a slit-like opening 8 is provided on the bottom portion of a magnetic field channel 16 along the outer circumference surface of the rotating drum 3. The opening 8 is provided, and thus, it is possible to increase recovery rates of the scrap, chips, or the like while maintaining the recovery rate of the ground particles.